The h-Sbx WO3+2x Oxygen Excess Antimony Tungsten Bronze

Abstract

We describe the previously unreported oxygen excess hexagonal antimony tungsten bronze is reported, with a composition of Sb_0.5 W₃ O₁₀ , in the following denoted as h-Sb_x WO_3+2x with x=0.167, to demonstrate its analogy to classical A_x WO₃ tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 °C<T<620 °C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-Sb_x WO_3+2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a=7.4369(4) Å and c=3.7800(2) Å. The antimony and excess oxygen occupy the hexagonal channels within the network of corner-sharing WO₆ octahedra. h-Sb_x WO_3+2x has a resistivity of ρ_{300 K} ≈1.28 mΩ cm at room temperature, with little if any temperature-dependence on cooling. DFT calculations on a simplified model for this compound find a metallic-like electronic structure with the Fermi level falling within rather flat bands, especially around the Γ point.

Keywords: antimony; bronze; hexagonal bipyramids; metallic oxide; tungsten.